1. Field of the Invention
The present invention relates to a crane having a non-cantilevered hydraulic extensible boom, and, more specifically, relates to a crane having a pendant supported hydraulic extensible boom.
2. Description of the Prior Art
It is known, as shown in the U.S. Pat. No. 4,053,058 (Jensen and Powers, Oct. 11, 1977) to provide a crane with a telescopic boom which is extended by cables and which is supported from a live mast by a pendant line.
It is also known to provide a crane with a cantilevered, telescopic boom, the sections of which are extended and retracted hydraulically, as shown, for example, in the U.S. Pat. No. 4,011,699 (Mickelson, Mar. 15, 1977). In the U.S. Pat. No. 3,856,151 (Lamer, Dec. 24, 1974), a cable is provided on a cantilevered, hydraulically operated telescopic boom to support a jib extension.
Yet other patents have combined the feature of hydraulic extension and retraction with a cable support of the boom (U.S. Pat. No. 3,371,799 of Brownell et al, Mar. 5, 1968; U.S. Pat. No. 2,868,392 of Poffenberger, Jan. 13, 1959; and U.S. Pat. No. 2,475,963 of R. C. Howell, July 12, 1949). In the patents U.S. Pat. No. 3,371,799; U.S. Pat. No. 2,868,392; and U.S. Pat. No. 2,475,963 the length of the boom supporting cable, or the elevation of the boom, is materially altered as the boom is extended or retracted, to accommodate the change in length of the boom.
U.S. Pat. No. 3,308,967 which issued to Barkley on Mar. 14, 1967, discloses a telescopic boom pivoted at its rear end having a live mast pivoted to the boom and substantially normal thereto. A fixed length pendant is secured at one end to the forward end of the tip section while the other end of the pendant is secured to the rear end of the tip section. The pendant is trained around a plurality of sheaves within the boom, around a sheave on the top of the mast, and is wrapped around a pair of driven wheels which provide the sole source for extending and retracting the boom. The boom is raised and lowered by a winch which drives a line connected to the upper end of a mast; and the mast may be pivoted intermediate its ends for reducing the height of the crane.